Tebentafusp Shows Durable Survival in Metastatic Uveal Melanoma, Immunocore Reports

Five-year overall survival (OS) data for tebentafusp-tebn (brand name Kimmtrak), a novel bispecific protein developed by Immunocore Holdings (Immunocore), show evidence that the therapy imparts long-term outcomes in metastatic uveal melanoma (mUM), a rare cancer historically associated with limited treatment options and poor prognosis, the company reported on April 19, 2026. The results, based on a phase 3 randomized trial, suggest a sustained survival benefit in previously untreated patients who are HLA-A*02:01-positive, a genetically defined subgroup.¹

Uveal melanoma remains the most common primary intraocular malignancy in adults, with up to half of patients developing metastatic disease. Historically, five-year survival rates in metastatic settings have been below 5%, underscoring the clinical challenge and unmet need in this indication. The newly reported data represent the longest follow-up from a randomized trial in this disease, as well as the longest reported for a T cell engager in a solid tumor.²

How does 5-year survival data reshape expectations in mUM?

Tebentafusp consists of a soluble T-cell receptor (TCR) fused to an anti-CD3 immune-effector function. In the study, 378 patients were randomized to receive tebentafusp (n=252) or investigator’s choice (n=126), with the majority of control-arm patients receiving pembrolizumab. At 5 years, OS was 16% in the tebentafusp arm compared with 8% in the control group, corresponding to a hazard ratio of 0.67. Median OS was 21.6 months versus 16.9 months, respectively.¹

According to the company, Kaplan–Meier survival curves separated early and remained distinct over time, suggesting durability of benefit. These findings may indicate a shift in expectations for long-term survival in metastatic uveal melanoma, for which durable outcomes have historically been rare.

“These important results allow us, for the first time, to speak with real confidence to patients about the possibility of long-term survival,” said Paul Nathan, consultant medical oncologist at Mount Vernon Cancer Center, UK, in a company press release.¹ “Before tebentafusp, such conversations simply weren't possible for metastatic uveal melanoma patients."

What do subgroup and post-progression findings suggest about treatment durability?

The survival benefit associated with tebentafusp was observed across multiple high-risk subgroups, including patients with elevated lactate dehydrogenase (LDH), high tumor burden, and extrahepatic disease. Notably, benefit was also reported in patients whose best overall response was progressive disease, including those with more than 20% tumor growth.¹

Treatment beyond progression appeared to play a role in outcomes. A higher proportion of patients in the tebentafusp arm continued therapy after progression compared with the control group (57% versus 25%). Among these patients, tumor reduction rates following continued treatment were higher in the tebentafusp arm (27% versus 4%), and extended post-progression survival was observed.

“These long-term overall survival results further solidify [Kimmtrak] as the first-line standard of care for HLA-A*02:01 positive patients with metastatic uveal melanoma,” said Mohammed Dar, MD, chief medical officer at Immunocore, in the release.¹ “The survival benefit was evident even in patients with known poor prognostic factors, including those with large tumors and extrahepatic disease.”

Could ctDNA and TCR-based therapies influence future immuno-oncology strategies?

Biomarker analyses from the study highlighted a potential role for circulating tumor DNA (ctDNA) in predicting outcomes. Patients with undetectable ctDNA at baseline or those achieving reductions of at least 50% by week 9 were associated with longer OS. Among patients surviving at least five years, a majority had either undetectable baseline ctDNA or early clearance, suggesting molecular response may provide a more sensitive measure of treatment activity than conventional imaging.¹

For the biopharmaceutical industry, these findings may reinforce interest in TCR-based platforms and bispecific approaches as a complement to existing checkpoint inhibitors. The durability of response, particularly in difficult-to-treat populations, could inform future clinical development strategies. However, further research will be needed to assess how these outcomes translate across broader patient populations and how biomarkers such as ctDNA can be integrated into clinical decision-making.³

The data from this phase 3 study were presented at the American Association for Cancer Research 2026 meeting.

References

1. Immunocore Holdings. KIMMTRAK doubles the likelihood of being alive at five years for first line HLA-A*02:01+ patients with metastatic uveal melanoma. Published April 19, 2026. Accessed April 20, 2026. https://www.immunocore.com/investors/news/press-releases/detail/129/kimmtrak-doubles-the-likelihood-of-being-alive-at-five-years-for-first-line-hla-a02-01-patients-with-metastatic-uveal-melanoma
2. Rantala ES, Hernberg M, Kivelä TT. Overall survival after treatment for metastatic uveal melanoma: a systematic review and meta-analysis. Melanoma Res. 2019;29(6):561-568. doi: 10.1097/CMR.0000000000000575 
3. Vimalathas G, Hansen MH, Cédile O, et al. Monitoring ctDNA in aggressive B-cell lymphoma: a prospective correlative study of ctDNA kinetics and PET-CT metrics. Blood Adv. 2025;9(20):5207-5218. doi: 10.1182/bloodadvances.2025016752